Even after Dynamic Web TWAIN HTML5 Edition has installed properly and works on earlier versions of Chrome or Firefox, it doesn't work anymore on Chrome 57+ or Firefox 53+ and keep prompting you to download and install it again on a secure page (SSL).
For the recommended solution, please check
If you don't wish to upgrade, then this is the temporary Solution
1. Open 'https://127.0.0.1:18619/' (for version 10.*, open 'https://localhost:18619/') in Chrome and you'll see the following
2. Chrome: Click 'Proceed to 127.0.0.1/localhost (unsafe)'. Firefox: Click 'Add Exception...'. Then you might see either one of the following messages.
"404 Not Found" (before v12.0)
"Configuration Information of Dynamic Web TWAIN Service" (v12.0)
3. Go back to your scan page and it should start working again.